using System;

using System.Threading;

using System.Threading.Tasks;

using System.Collections.Generic;

using System.Linq;

​

using System.Diagnostics;

using LanguageExt;

​

public class Program

{

    public static async Task Main(string[] args)

    {

        Console.WriteLine(ToResponse<Value>(new HaveASandwich(null, true)).Result);

        Console.WriteLine(ToResponse<Value>(new HaveASandwich("error", true)).Result);

        Console.WriteLine(ToResponse<Value>(new HaveASandwich("no error", false)).Result);

        Console.WriteLine(ToResponse<Value>(new HaveASandwich("null", false)).Result);

        //Console.WriteLine(ToResponse2<Value>(new HaveASandwich(null, true)).Result);

        //Console.WriteLine(ToResponse2<Value>(new HaveASandwich("error", true)).Result);

        //Console.WriteLine(ToResponse2<Value>(new HaveASandwich("no error", false)).Result);

        //Console.WriteLine(ToResponse2<Value>(new HaveASandwich("null", false)).Result);

    }

    public static async Task<Either<Error, T>> ToResponse<T>(HaveASandwich a) where T : new(){

        var content = await a.ReadAsStringAsync();

        if (string.IsNullOrEmpty(content))

        {

            return new Error();

        }

​

        return a.IsError() switch

        {

                true => DeserializeError(content) ?? new Error(),

                false => DeserializeValue<T>(content) ?? throw new InvalidOperationException("Error while handling HttpResponseMessageExt ToResponse DeserializeValue")

        };

    }

    public static Task<Either<Error, T>> ToResponse2<T>(HaveASandwich a) where T : new(){

        return a.ReadAsStringAsync().ContinueWith(t =>

                ((Either<Error, string>)t.Result)

                    .Bind<string>(v => string.IsNullOrEmpty(v) ? new Error() : v)

                    .Bind<T>(v => a.IsError() ? DeserializeError(v) : DeserializeValue<T>(v))

        );

    }

    public static Error DeserializeError(string c){

        return new Error();

    }

    public static T DeserializeValue<T>(string c) where T : new(){

        return c == "null" ? default(T) : new T();

    }

}

public class HaveASandwich{

    private string Result;

    private bool Error;

    public HaveASandwich(string r, bool e){

        Result = r;

        Error = e;

    }

    public async Task<string> ReadAsStringAsync(){

        return Result;

    }

    public bool IsError(){

        return Error;

    }

}

​

public class Error{ 

}

​

public class Value{

}